1. Field of the Invention
The present invention relates to a display device and a manufacturing method thereof and more particularly to a display device in which a plurality of pixels and a drive circuit that drives the pixels are formed above a substrate and a manufacturing method thereof.
2. Background Art
Conventional liquid crystal display devices include a first substrate on which pixel electrodes and the like are formed, a second substrate disposed so as to face the first substrate, and a liquid crystal layer interposed between the first substrate and the second substrate. On the first substrate, in each of regions surrounded by a plurality of gate lines extending in the x-direction and arranged in parallel in the y-direction and a plurality of drain lines extending in the y-direction and arranged in parallel in the x-direction for example, a pixel is configured to include at least a thin film transistor controlled by a scanning signal from the gate line and the pixel electrode supplied with a video signal from the drain line via the thin film transistor. With this configuration, each of the pixels can be controlled independently, so that an image is displayed by these pixels. On the second substrate, a black matrix and color filters of R (red), G (green), and B (blue) corresponding to each of the pixels are formed, so that color display is performed according to the transmission amount of light transmitting the color filters.
On the other hand, a technique of forming a low-temperature polysilicon TFT (LTPS) as a thin film transistor has been established, and the LTPS is used as a thin film transistor for switching disposed in each of pixels. Further, it has become general to form a video signal drive circuit (drain driver) or a scanning signal drive circuit (gate driver) above the first substrate by using the LTPS. Along with an increase in the number of LTPSs formed in one liquid crystal display device as described above, the possibility of electrostatic breakdown of the LTPS is also increased in the course of the manufacture.
As a technique of protecting a thin film transistor against electrostatic breakdown, there is a liquid crystal display device disclosed in Patent Document 1, for example. In the liquid crystal display device disclosed in Patent Document 1, a capacitive electrode having a wide width is formed parallel to a gate bus line in a region near the side of a substrate, and after depositing a gate insulating layer, an end portion of a drain bus line formed on the film is formed so as to extend over the capacitive electrode. In a final stage of the manufacturing process, the region near the side is cut from the substrate, so that the drain bus line and the end portion are separated from each other.
Patent Document 1: Japanese Patent No. 3089818